Radiation terephthalate

Polyimide. Polyimide is a biaxiaHy oriented high performance film that is tough, flexible, and temperature- and combustion-resistant. Its room temperature properties compare to poly(ethylene terephthalate), but it retains these good characteristics at temperatures above 400°C. Its electrical resistance is good and it is dimensionally stable. The principal detriment is fairly high moisture absorbance. The main uses are for electrical insulation, particularly where high temperatures are prevalent or ionizing radiation is a problem. The films may be coated to reduce water absorption and enhance... 

Lead sesquioxide is used as an oxidation catalyst for carbon monoxide ia exhaust gases (44,45) (see Exhaust control), as a catalyst for the preparation of lactams (46) (see Antibiotics, P-lactams), ia the manufacture of high purity diamonds (47) (see Carbon, diamond-natural), ia fireproofing compositions for poly(ethylene terephthalate) plastics (48), ia radiation detectors for x-rays and nuclear particles (49), and ia vulcanization accelerators for neoprene mbber (50). 

Detection and result The chromatogram was dried in a stream of warm air for 10 min, immersed in the reagent solution for 3 s and then subjected to intense UV radiation (high pressure lamp, A = 365 nm) for up to 10 min. Terephthalic (hRf 0 - 5), pimelic (hRf 55), suberic (hRf 60), sebacic (hRf 65 — 70) and benzoic acids (hRf 70 — 75) together with sorbic, malic, adipic, citric, tartaric, lactic and fumaric acids only exhibited a reaction on silica gel layers at higher concentrations. 4-Hydroxybenzoic, salicylic and acetylsalicylic acids fluoresced light blue after irradiation. The detection limit per chromatogram zone was 0.5 pg for salicylic acid and more than 5 pg for benzoic acid. 

The poly(ethylene terephthalate-co-esters) were prepared as previously described (9) after knitting, scouring, and deknitting, the yarns were examined, tested and exposed in a standard fashion (9) to 3000 A radiation. 

Figure 4. Effect of radiation on the poly(ethylene terephthalate-co-2,6-naphthalene-dicarboxylate) yarns mole % of 2,6-DMN (%) 0.0 (X) 0.5 fA) 1-0 (O) 2.0 ...

Photophysical Processes in Pol,y(ethy1eneterephthalate-co-4,4 -biphenyldicarboxyl ate) (PET-co-4,4 -BPDC). The absorption and luminescence properties of PET are summarized above. At room temperature the absorption spectrum of PET-co-4,4 -BPDC copolymers, with concentrations of 4,4 -BPDC ranging from 0.5 -5.0 mole percent, showed UV absorption spectra similar to that of PET in HFIP. The corrected fluorescence spectra of the copolymers in HFIP exhibited excitation maxima at 255 and 290 nm. The emission spectrum displayed emission from the terephthalate portion of the polymer, when excited by 255 nm radiation, and emission from the 4,4 -biphenyldicarboxylate portion of the polymer when excited with 290 nm radiation. 

As the concentration of 4,4 -BPDC increases, an increase in the intensity of the band at 289.5 nm was observed. This is the result in the increased intensity of the A - lL- transition of the 4,4 -BPDC in this region. In dilute HFIP solutions the copolymers show a fluorescent emission in the 326 - 338 nm range when excited with 255 nm radiation. This emission corresponds to emission from the terephthalate units of the copolymer. 

However, excitation with 290 nm radiation produces an emission that is red shifted relative to the terephthalate emission. 

In the yarns, the fluorescence of the 4,4 -biphenyldicarboxy-late unit is distinct and predominate both at 298 and 77°K. Examination of the phosphorescence spectra of the PET and PET-co-4,41-BPDC yarns revealed three emission maxima. In the PET homopolymer excitation with 310 nm radiation produced an emission at 452 nm from the terephthalate chromophore. In the copolymers excitation with either 305 or 310 nm radiation produced emission spectra with distinct maxima at 480 and 515 nm (t 1.2 sec), and a shoulder near 452 nm (t = 1.2 sec). The maxima in the phosphorescence spectra were assigned as emission from the 4,4 -biphenyldicarboxylate units of the copolymer. The observed emissions are bathochromatically shifted from the emission of 4,4 -BPDC in a glassed solvent. This is supported by the observed emissions from solid 4,4 -BPDC at 520 and 560 nm (t =. 3 sec) when excited with 340 or 356 nm radiation. 

Example PET. Let us consider polyethylene terephthalate) (PET, C oHK(h n, Ppet=1-35 g/cm3) of tpET =2 mm thickness and an X-radiation wavelength X= 0.15418 nm (CuKa). We set up a table with one row for each chemical element and sum both the masses and the mass absorption coefficients multiplied by the masses. After normalization to the molecular mass of the PET monomer, 192.17 amu, we find (p/p)pet = 1291.97/192.17 cm2/g a value 6.72 cm2/g. Considering the density ppet we find for the linear absorption coefficient Ppet =... 

Radiation initiated or photodegradation - free radical reactions (see Chapter 18 on photodegradation and photostabilization of poly (ethylene terephthalate)). 

Table 9.5 lists the uses of ethylene oxide. Ethylene glycol is eventually used in two primary types of end products polyesters and antifreeze. About half the ethylene glycol is used for each end product. Poly(ethylene terephthalate) is the leading synthetic fiber and has other important applications in plastic film and bottles. Ethylene glycol is a common antifreezing agent especially in automobile radiators. 

T wo aspects of the radiation chemistry of polyethylene terephthalate (PET) are reviewed here the dependence of product yields on radiation dose and on dose rate. The review is limited to work with thin films from which air and water were pumped prior to irradiation. Moreover, it is judged that in the experiments described postirradiation effects were negligible. 

Polystyrene itself is not used for endoprosthetic purposes and its application is accounted for only because of easy substitutions in benzene rings. The method was subsequently modified for heparinization of silicone and natural rubber, polyethylene, polypropylene, polyethylene terephthalate), and other polymers. Styrene was first grafted onto the polymers by y-radiation and then the above-described reaction was performed in the second step. All the polymers synthesized in this way contained sufficiently large amounts of immobilized heparin (2.8—15.7 ng/cm2) and displayed good thromboresistance when tested in vitro — recalcified blood was not clotted for several hours. 

Blends of iso- and terephthalates give amorphous, transparent resins, mosdy yellow in color. Heat-deflection temperatures are higher than those of 100% PC resins and depend on the iso- to terephthalate ratio. For example, a resin with a 1 1 ratio has a value of 160°C. These resins are flame retardant mechanical and electrical properties are similar to those of PC resins. The notched Izod impacts are lower at 150—300 J/m (4.7—5.6 fflbf/in.), even in thick sections. Long-term uv radiation stabilities are excellent, but yellowness increases during initial exposure owing to photo-Fries rearrangements (80), wherein 0-hydroxy-benzophenone units are produced along the polymer chains. 

Mark G, Schuchmann MN, Schuchmann H-P, von Sonntag C (1990) The photolysis of potassium peroxodisulphate in aqueous solution in the presence of tert-butanol a simple actinometer for 254 nm radiation. J Photochem Photobiol A Chem 55 157-168 Mark G, Korth H-G, Schuchmann H-P, von Sonntag C (1996) The photochemistry of aqueous nitrate revisited. J Photochem Photobiol A Chem 101 89-103 Mark G, Tauber A, Laupert R, Schuchmann H-P, Schulz D, Mues A, von Sonntag C (1998) OH-radical formation by ultrasound in aqueous solution, part II. Terephthalate and Fricke dosimetry and the influence of various conditions on the sonolytic yield. Ultrason Sonochem 5 41-52 MarkG, Schuchmann H-P, von Sonntag C (2000) Formation of peroxynitrite by sonication of aerated water. J Am Chem Soc 122 3781-3782... 

Matthews RW (1980) The radiation chemistry of the terephthalate dosimeter. Radiat Res 83 27-41 Merga G, Schuchmann H-P, Rao BSM, von Sonntag C (1996) OH-Radical-induced oxidation of chlorobenzene in aqueous solution in the absence and presence of oxygen. J Chem Soc Perkin Trans 2 1097-1103... 

Saran M, Summer KH (2000) Assaying for hydroxyl radicals hydroxylated terephthalate is a superior fluorescence marker than hydroxylated benzoate. Free Rad Res 31 429-436 Scholes ML, Schuchmann MN, von Sonntag C (1992) Enhancement of radiation-induced base release from nucleosides in alkaline solution essential role of the O- radical. Int J Radiat Biol 61 443-449... 

Ablation using radiations of various wavelengths (IR, visible, UV, or x-ray) has been employed to fabricate plastic chips. For instance, photoablation using pulsed UV lasers (193 nm) has been used to fabricate plastic chips out of polyethylene terephthalate (PET, 100 pm thick) [189,190, 258,758] and polycarbonate (PC, 125 pm thick) [189,258]. Channels as narrow as 30 pm and as deep as 100 pm can be made [258,758]. The cross section of a photoablated PET channel plate laminated with another PET using a thin PE adhesive layer was shown in Figure 2.20 [191]. 

Balabanovich AI, Zevaco TA, Schnabel W. Fire retardance in polyfbutylene terephthalate). The effects of red phosphorus and radiation-induced cross-links. Macromol. Mater. Eng. 2004 289 181-190. 

A similarly poor efficiency in extraction can also be seen in Fig. 11, where the extraction result for the product obtained by the radiation grafting of styrene onto polyethylene terephthalate)(PET) fibers13 is shown. In this case the unreacted PET can be extracted after most of PS homopolymer has been extracted by repeated solution-precipitation of the sample. It should be mentioned here that the solution procedure is also necessary to extract the unreacted PET. Such a solution-precipitation procedure is also necessary for nylon-styrene13 and poly(vinyl chloride)-acrylo-nitrile14 graft products so as to remove the homopolymers to a sufficient extent. 

Polyethylene terephthalate film (Mylar) is often used at cryogenic temperatures for electrical- or thermal insulation, as described in the preceding section. However, the radiation tolerance of Mylar is rather poor as shown in Fig. 5. Takamura and Kato reported that Mylar was too brittle to handle after irradiation of 6.2 x 106 Gy at 5 K [45]. 

Various polyesters derived from phosphorous or phosphoric acids were prepared. Efiicient polyphosphites were synthesised in the early 196(. Polyphosphite prepared from 152 and 4,4 -isopropylidenebis(cyclohexanol) was tested as a thermal stabilizer for PC [199] or as secondary AO for radiation sterilized EPM [200]. Built-in phosphites obtained by transesterification of triallcylphosphite with 4,4 -isopro-pylidenebisphenol or 4,4 -thiobisphenol possess antioxidant properties in polyolefins. Stabilizer containing phosphite moiety 153 was prepared from tris(2-hydroxy-ethyl)isocyanate, decyl alcohol and triphenylphosphite [201]. Various phosphites were derived firom polynuclear phenols or dihydric phenols. For example, a polycondensate prepared by reaction of phosphorus trichloride with 2,5-di-rert-butylhydroquinone was tested as heat and light stabilizer for PP [202], A linear polyester with a built-in phenolic moiety was synthesised from (2,6-di-tm-butyl-4-methylphenyl)bis(6-hydroxyhexyl)phosphite and dimethyl terephthalate [203]. 

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